ID?

It's a slimehead (Trachichthyidae) but there's about fifty species in several genera, and lots of them are very similar (and most of them I have no idea what they actually look like). Probably a Hoplostethus or Gephyroberyx though.

@Chlidonias Thanks!. The only species listed being ever kept in Europe on ZTL (most probably outdated) is Gephyroberyx japonicus so that could be an option...

Gephyroberyx japonicus. It's the only slimehead kept in aquariums AFAIK. Gephyroberyx darwinii is similar but I am not aware of it being kept (it is likely synonymous with G. japonicus anyway).

@DaLilFishie "It's the only slimehead kept in aquariums AFAIK."
Well that would depend on where the aquarium is located, e.g. an older photo of mine:
common roughy (Paratrachichthys trailli) - ZooChat

@Chlidonias oh damn, didn't know that species was kept. very cool!